Literally needless to emphasize, serious defects in wound or wrapped, multilayer supply rolls of various plastic film products arise from various wrinkles (including the so-called "knots" caused by large wrinkles as well as small, hard wrinkles in the rolled-up film product), die lines, seams, air knife and the like lines, foreign material(s) included in the wrapping plies, etc. These, upon attempted dispensation of such imperfectly wound roll packages, tend to cause tearing into strips of the film end being released from the supply or, in even more drastic consequence, complete failure of film dispensing capability.
As limited and restricted as it is, the presently known and utilized technique for quality control testing of wrinkles in wound supply rolls of plastic film by and large consists of visual spot checking which, unavoidably, is subject to qualitative and personalized judgment. In such procedure, correlations between wrinkle (and other imperfection size) and product failure in the indicated particulars have ordinarily been incapable of achieving overall or 100 percent on-line roll inspection concluding of the manufacturing process.
Typical of the plastic films involved in such manufacturing quality control difficulties are "HANDI-WRAP".TM. Brand polyolfin film and "SARAN WRAP ".TM. Brand saran film, both of which are commercially made by and available from The Dow Chemical Company of Midland, Mich. 48640. Of course, many other analogous and similar plastic film products are beset by the same problems insofar as concerns quality control procedures in their manufacture.
There are a number of known arrangements in which laser beams are utilized for quality control and flaw-detection purposes in various materials, including plastic goods. Among these are those shown in U.S. Pat. Nos.: 3,771,171 (to Hollenbeck); 3,792,930 (to Obenreder); 3,807,870 (to Kalman); 3,843,890 (to Anthony et al.); 4,017,194 (to Conroy et al.); 4,136,961 (to Young); 4,162,125 (to Schmidt); 4,197,457 (to Cheo); and 4,208,126 (to Cheo et al.).
Of these, the Patent to Cheo et al.; the same pertaining to the detection of flaws in polyethylene insulated cable through the use of a laser and a detector. The Cheo reference is somewhat more generally directed to the subject of detecting flaws in plastics, again with use of a laser and a detector.
Nothing in the prior art, however, appears to realistically concern itself with nor teach nor lead to an effective, efficient and extremely reliable means and technique, well-adapted for production line application and usage, for accurate wrinkle and other flaw testing in quality control inspection and observation of wound supply rolls of plastic film product using laser beam means in the implementation as in the way so crucially indigenous as is in the present contribution to the art.